Field of the Invention
The present invention relates to laser endovascular treatments, and more particularly, to the treatment of vascular pathologies, such as venous insufficiency, with laser energy using an optical fiber.
Information Disclosure Statement
The human venous system of the lower limbs consists essentially of the superficial venous system and the deep venous system, both connected by perforating veins. The superficial system comprises the great and the small saphenous veins, while the deep venous system includes the anterior and posterior tibial veins, which converge to form the popliteal vein near the knee. The popliteal vein, in turn, becomes the femoral vein when joined by the small saphenous vein.
The venous system comprises valves that function to achieve unidirectional blood flow back to the heart. Venous valves are bicuspid valves wherein each cusp forms a blood reservoir. The bicuspid venous valves force their free surfaces together under retrograde blood pressure. When properly operating, retrograde blood flow is prevented, allowing only antegrade flow to the heart. A bicuspid valve becomes incompetent when its cusps are unable to seal properly under a retrograde pressure gradient such that retrograde blood flow occurs. When retrograde blood flow occurs, pressure increases in the lower venous sections which can, in turn, dilate veins and lead to additional valvular failure.
Valvular failure, usually referred to as venous insufficiency, is a chronic disease that can lead to skin discoloration, varicose veins, pain, swelling and ulcerations. Varicose veins are blood vessels that have become enlarged and twisted and have progressively lost elasticity in their walls. Due to the widening of the blood vessels, the valves cannot be completely closed and the veins lose their ability to carry blood back to the heart. This leads to an accumulation of blood inside the vessels which can, in turn, further enlarge and twist the veins. Varicose veins usually have a blue or purple color and may protrude in a twisted form above the surface of the skin giving rise to a characteristically unattractive appearance. Varicose veins are commonly formed in the superficial veins of the legs, which are subject to high pressure when standing. Other types of varicose veins include venous lakes, reticular veins and telangiectasias.
There are a number of treatments available for eradicating these types of vascular pathologies. Some such treatments only operate to relieve certain symptoms but do not eliminate the varicose veins or prevent them from reforming. These treatments include elevating the legs by lying down or using a footstool when sitting, elastic stockings and exercise.
Varicose veins are frequently treated by eliminating the insufficient veins. These treatments force the blood that otherwise would flow through the eliminated vein to flow through the remaining healthy veins. Various methods can be used to eliminate problematic insufficient veins, including surgery, sclerotherapy, electro-cautery, and laser treatments.
Sclerotherapy uses a fine needle to inject a solution directly into the vein. This solution irritates the lining of the vein, causing the lining to swell and the blood to clot. The vein turns into scar tissue that may ultimately fade from view. Some physicians treat both varicose and spider veins with sclerotherapy. Today, commonly used sclerosants include hypertonic saline or Sotradecol™ (sodium tetradecyl sulfate). The sclerosant acts upon the inner lining of the vein walls to cause them to occlude and block blood flow. Sclerotherapy can give rise to a variety of complications. People with allergies may suffer allergic reactions which at times can be severe. If the needle is not properly inserted, the sclerosant can burn the skin or permanently mark or stain the skin. In addition, sclerotherapy can occasionally lead to blood clots or traveling blood clots. According to some studies, larger varicose veins may be more likely to reopen when treated with sclerotherapy, and therefore sclerotherapy treatments are generally limited to veins below a particular size.
Vein stripping is a surgical procedure used to treat varicose veins under general or local anesthesia. The problematic veins are stripped from the body by passing a flexible device through the vein and removing it through an incision near the groin. Smaller tributaries of these veins also are stripped with such a device or are removed through a series of small incisions (e.g., by ambulatory phlebectomy). Those veins that connect to the deeper veins are then tied off.
One drawback of vein stripping procedures is that they can cause scarring where the incisions are made and occasionally may cause blood clots. Another drawback is that vein stripping can be painful, time consuming to perform, and can require lengthy recovery periods. Yet another drawback of vein stripping procedures is that they can damage collateral branches of the stripped vein which may bleed and, in turn, give rise to hematomas, or lead to other complications, such as blood loss, pain, infection, nerve injury and swelling. Yet another drawback of vein stripping is that because of the damage done to the treated area, patients may have pain and discomfort for many hours, if not many days following surgery. Another drawback of vein stripping procedures is that they can include other negative side effects associated with performing such surgical procedures under anesthesia, including nausea, vomiting, and the risk of wound infection.
Another well known method of treating insufficient veins is through the use of radio frequency (“RF”). An exemplary RF method is described in U.S. Patent Application No. 2006/0069471 to Farley et al. Electrodes are introduced through a catheter inside the vein, the electrodes are placed in contact with the vein wall, and RF energy is applied through the electrodes to selectively heat the vein wall. RF energy is applied in a directional manner through the electrodes and into the portions of the vein wall that are in contact with the electrodes to cause localized heating and fibrosis of the venous tissue. One drawback of RF methods is that they require maintained contact between the RF electrodes and the vein wall and thus deliver energy to the vein wall essentially only through such points of contact. Yet another drawback of RF methods is that they can be more time consuming and thus more stressful to the patient than otherwise desired. Yet another drawback of RF methods is that the RF catheters and electrodes can be relatively complex and more expensive to manufacture than otherwise desired.
Another minimally invasive prior art treatment for varicose veins is endoluminal laser ablation (“ELA”). In a typical prior art ELA procedure, an optical fiber is introduced through an introducer sheath into the vein to be treated. The fiber optic line has a flat emitting face at its distal end. An exemplary prior art ELA procedure includes the following steps: First, a guide wire is inserted into the vein to be treated, preferably with the help of an entry needle. Second, an introducer sheath is introduced over the guide wire and advanced to a treatment site. Then, the guide wire is removed leaving the introducer sheath in place. The optical fiber (coupled to a laser source) is then inserted through the introducer sheath and positioned so that the flat emitting face at the distal tip of the fiber and the sheath are at the same point. Tumescent anesthesia is then applied to the tissue surrounding the vein to be treated. Prior to lasing, the sheath is pulled back from the flat emitting face a distance sufficient to prevent the emitted laser energy from damaging the sheath. Then, the laser is fired to emit laser energy through the flat emitting face and into the blood and/or vein wall directly in front of the emitting face. While the laser energy is emitted, the laser fiber and introducer sheath are withdrawn together to treat and close a desired length of the vein. The laser energy is absorbed by the blood and/or vein wall tissue and, in turn, thermally damages and causes fibrosis of the vein.
U.S. Pat. No. 6,200,332 to Del Giglio discloses an exemplary prior art device and method for under skin laser treatment with minimal insertions into the area of treatment. Common vascular abnormalities such as capillary disorders, spider nevus, hemangioma, and varicose veins can be selectively eliminated. A needle is inserted into the vascular structure and the targeted abnormalities are subjected to emitted laser radiation. The device allows for orientation and positioning of the laser delivering optical fiber during treatment. An extension piece maintains the optical fiber in a fixed position relative to, and at a fixed distance from, a hand piece to allow the user to know the extent to which the fiber has been inserted into the vein.
U.S. Pat. No. 6,398,777 to Navarro et al. describes another ELA procedure in which percutaneous access into the vein lumen is obtained using an angiocatheter through which a fiber optic line is introduced. The fiber optic line has a bare, uncoated tip defining a flat radiation emitting face. The '777 patent teaches manually compressing the vein, such as by hand or with a compression bandage, to place the vein wall in contact with the flat emitting face of the fiber tip. The laser energy is delivered in high energy bursts into the portion of the vein wall in contact with the bare fiber tip. The wavelength of the laser energy is in the range from about 532 nm to about 1064 nm and the duration of each burst is about 0.2 seconds to about 10 seconds. Each burst delivers from about 5 watts to about 20 watts of energy into the vein wall. The '777 patent and other prior art ELA procedures teach delivering sufficient energy to insure damage to the entire thickness of the vein wall to ultimately result in fibrosis of the vein wall and occlusion of the greater Saphenous vein.
Consistent with the '777 patent, the prior art teaches applying relatively high energy levels (e.g., ≧80 J/cm) in order to improve the treatment success of ELA of incompetent Saphenous veins. Timperman et al. teach that endovenous laser treatments of the Saphenous vein are particularly successful when doses of more than 80 J/cm are delivered. Timperman et al. collected data regarding the length of treated vein and the total energy delivered on 111 treated veins. The wavelength of laser energy applied was 810 nm or 940 nm. Of the 11 treated veins, 85 remain closed (77.5%) during the follow-up period. In this group of successfully treated veins, the average energy delivered was 63.4 J/cm. For the 26 veins in the failure group, the average energy delivered was 46.6 J/cm. No treatment failures were identified in patients who received doses of 80 J/cm or more. P. Timperman, M. Sichlau, R. Ryu, “Greater Energy Delivery Improves Treatment Success Of Endovenous Laser Treatment Of Incompetent Saphenous Veins”, Journal of Vascular and Interventional Radiology, Vol. 15, Issue 10, pp. 1061-1063 (2004).
One drawback associated with this and other prior art ELA treatments is that the laser radiation is applied only through the very small flat emitting face at the bare fiber tip. As a result, substantially only a very small, localized portion of the blood and/or vein wall in front of the flat emitting face directly receives the emitted laser energy at any one time. Yet another drawback of such prior art ELA devices and methods is that the laser radiation is directed only in a forward direction out of the flat emitting face of the fiber. Accordingly, substantially no radiation is emitted radially or laterally from the fiber tip thereby delivering the laser radiation in a relatively localized manner. A further drawback is that the relatively high levels of energy delivered into the vein create significantly increased temperatures which can, in turn, give rise to corresponding levels of pain in the surrounding tissues. The relatively high levels of energy delivered also can give rise to corresponding levels of thermal damage in surrounding tissues. The more intense the thermal damage, the greater is the chance for post procedure pain, bruising and the possibility of paresthesia. Paresthesia is an abnormal and/or unpleasant sensation resulting from nerve injury. Yet another drawback is that such relatively high levels of energy delivery and/or localized concentrations of laser radiation can give rise to vein perforations. As a consequence, such prior art ELA procedures can require relatively high levels of anesthetic, such a local tumescent anesthesia, more time, and can give rise to more stress to both a patient and physician, than otherwise desired.
A further drawback of prior art ELA treatments is that they employ a tumescent technique involving substantial volumes of tumescent anesthesia. For example, a typical prior art ELA treatment employs at least about 100 ml to about 300 ml or more of tumescent anesthesia depending on the length of vein to be treated. The tumescent anesthesia is injected into the tissue along the length of the vein. In some cases, the tumescent anesthesia is injected into a perivenous cavity defined by one or more fascial sheaths surrounding the vein. In other cases, the tumescent anesthesia is injected into the leg tissue surrounding the vein. Tumescent anesthesia typically consists essentially of dilute concentrations of Lidocaine and Epinephrine in a saline solution. One drawback of such tumescent techniques is that the anesthetic is toxic, and in some cases when, for example, substantial volumes are employed, the anesthetic can cause adverse patient reactions, such as convulsions. Yet another drawback of the tumescent technique is that patients can experience an undesirable elevation in blood pressure due to the use of Epinephrine. A still further drawback of the tumescent technique is that it requires the injection of substantial volumes of liquid anesthetic along the length of the vein, which adds a significant amount of time to the overall ELA procedure, and can give rise to adverse post treatment side effects, such as black and blue marks, and other adverse effects associated with such large volumes of anesthetic.
Although the tumescent anesthesia or cold saline tumescent infusion used in the tumescent technique of prior art ELA procedures creates a heat sink surrounding the vein, it can allow for significantly higher levels of thermal damage to the surrounding tissues than desired. The more intense the thermal damage the greater is the chance for post procedure pain, bruising, and the possibility of paresthesia. For example, the significant quantities of tumescent anesthesia employed in prior art ELA procedures typically will prevent a patient from feeling any thermal stimulation of the nerves, and therefore will prevent the patient from alerting the physician to stop or adjust the procedure to prevent undesirable thermal damage. The tibial nerve (TN) and its common peroneal nerve (CPN) branch both are subject to the possibility of such damage. The CPN is very superficial in the lateral leg just below the knee, and thermal damage to this nerve can lead to foot drop. Similarly, the TN is subject to the possibility of thermal damage when exploring high in the popliteal fossa. Depending on its extent, thermal damage to the TN can lead to muscle dysfunction of the calf and foot muscles. The sural nerve (SUN) and Saphenous nerve (SAN) likewise are subject to the possibility of thermal damage when performing ELA of the small Saphenous vein (SSV) or the GSV below the knee. The SUN runs very close to the SSV especially distally closer to the ankle. The SAN runs very close to the GSV below the knee especially, again, distally closer to the ankle. Significant quantities of anesthesia, such as tumescent anesthesia, can unknowingly lead to thermal damage of such nerves.
U.S. Pat. No. 6,986,766 relates to the application of markings on an optical fiber to determine fiber position relative to an introducer sheath. However, this and other related inventions lack information to determine pullback speed of a laser fiber while lasing. Slow uncontrolled pullback of the laser fiber or catheter can be cause for overheating and perforation of the vessel wall, as even the best surgeon may have difficulty retracting the fiber at exactly the correct speed to maintain an appropriate vessel wall heating temperature. On the other hand, excessive pullback speed may result in insufficient irradiated energy for proper vessel occlusion.
U.S. Patent Application No. 2004/0199151 to Neuberger, which is assigned to the Assignee of the present invention, and is hereby incorporated by reference in its entirety as part of the present disclosure, discloses a system and method for controllably releasing radiation in percutaneous radiation treatments. A laser is coupled to an optical fiber that is inserted below the skin or into a vascular lumen to a predetermined point. Radiation is then delivered to the treatment site while the fiber is simultaneously withdrawn toward the entry point. The fiber is manually withdrawn at a predetermined rate and radiation is administered in a constant power or energy level. To maintain a constant desired energy density, the speed of withdrawal is measured and sent to a controlling mechanism. The controlling mechanism modifies the power emitted, pulse length or pulse rate to ensure that the vein or tissue receives a consistent dose of energy. Although this is a considerable improvement over the prior art, the radiation is emitted through a flat emitting face located at the fiber tip and primarily in a longitudinal direction.
Accordingly, it is an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of the prior art.